THE NERVOUS SYSTEM OP ANTEDON ROSACEUS. 289 



to the mouth. Furthermore, the subepithelial band is in very intimate 

 relation with that most characteristic Echinoderm system, the ambu- 

 lacral vessels and their prolongations into the tentacles. 



Seeing, then, that there are along the ventral surface of the arms 

 structures of great importance in very close anatomical relation with 

 these subepithelial bands, which agree histologically with what are 

 undoubtedly nerves, it seems probable that these bands form a special 

 part of the nervous system connected with one or other, or perhaps 

 all of these special structures. 



That the connection between the subepithelial bands and the 

 ambulacral epithelium and tentacles is a very intimate one is shown 

 by P. H. Carpenter's observation, alluded to above, that in both 

 Antedon and Actinometra all three structures disappear together, 

 both in the oral pinnules and in those arms or portions of arms 

 which are devoid of ambulacral grooves. 



G. Summary of Results. 



1. The central capsule, and its prolongations the axial cords and 

 their branches, constitute the main nervous system of Antedon. 



2. The central capsule is specially connected with the complex 

 co-ordinated movements of swimming and of righting when inverted. 



3. The axial cords act as both afferent and efferent nerves. 



4. The subepithelial bands are probably also nerves, but their exact 

 function, probably a special and subordinate one in connection with 

 the ambulacral tentacles and epithelium, is not yet ascertained. 



5. Evisceration apparently causes but little inconvenience to the 

 animal, and the visceral mass is regenerated completely in a few 

 weeks' time. 



These results are in complete accordance with the views so stead- 

 fastly advocated for many years past by the Carpenters, and recently 

 adopted by Perrier; while, on the other hand, they are in direct 

 opposition to the tenets of the German school. 1 



IV. Morphological Considerations. 

 Certain points of very considerable morphological interest arise in 



1 Since this paper was written Dr. Jickeli, of Jena, has published an account of experiments 

 made on the nervous system of Antedon, which lead him to strongly uphold the correctness 

 of Dr Carpenter's views. Many of Jickeli' s experiments are identical with ones described 

 above, and his paper, (' Zoologischer Anzeiger,' 23rd June, 1884) although at present incom- 

 plete, contains much valuable information, 



U 



